I'm confused.. you have a p/g thats got at least 2-3k's in it..
but worried what a good built 2004r will be..
if it was my chevelle.. (I had4 and 1 elcamino)
I'd sell the fresh p/g and get a built th350 or th400 and the g/v
and you'll have 6 gears
no idea where you are from.. but art carr is on the west coast and there are 2004r builders on the east coast..
g body's guys flog the crap out of them..
like your p/g . it needs aftermarket stronger hard parts... to live..
a 4l80e that you don't want is a th400 with a o/d on the back..
the 7004r/4l60e the o/d is in the front..
the 700 has a mile long drop from 1st to 2nd gear..
for the money you are going to drop.. why not drop a tremic 5 speed in it..
they have bolt in kits for these cars.. and with hyd clutch won't pound on your knees